Pyrimidine Nucleosides, Benzoic Acid Derivative, and Bipyridine From the Marine-Derived Streptomyces Sp. DS52

Fourteen new compounds were isolated from marine-derived Streptomyces sp. DS52, including 12 pyrimidine nucleosides (1-12), 1 benzoic acid derivative (13), and 1 dipyridine derivative (14). Additionally, 28 known compounds (15-42) were identified. The structures of all compounds were elucidated through extensive analysis of nuclear magnetic resonance spectroscopic and high-resolution electrospray ionization mass spectroscopy data. Electronic circular dichroism (ECD) calculations were employed to investigate the configurations of compounds 1, 2, and 4-13. Bioactivity evaluations of all of the compounds showed that compound 41 exhibited significant cytotoxicity against the HCT-116 and MDA-MB-231 human cancer cell lines with IC₅₀ values of 0.73 ± 0.06 and 1.11 ± 0.06 µM, respectively. Notably, compounds 6, 7, 9, 11, 15, 33-38, 41, and 42 exhibited cytotoxicity against HCT-116 human colon cancer cell lines and MDA-MB-231 human breast cancer cell lines, with IC₅₀ values ranging from 0.73 ± 0.06 to 17.44 ± 0.53 µM and from 1.11 ± 0.06 to 18.51 ± 3.07 µM, respectively.